Westone 3 in-ear headphones Measurements
Deciding what, exactly, is the optimal frequency response for a pair of headphones is neither obvious nor trivial (see www.stereophile.com/features/808head). The only measurement I perform on headphones, therefore, is of their electrical impedance, to determine how difficult they are to drive.
The Weston 3's impedance and electrical phase are shown in fig.1. (The headphones were inserted in my ears for this measurement.) The impedance is close to the 30-ohm specification, though it reaches minimum values of 22 ohms in the midrange and 16 ohms in the presence region, and a maximum of 47 ohms at 1400Hz. While this earphone will be a little demanding of current, this will be ameliorated by its fairly high specified sensitivity, and it should work well with iPods. However, the low bass will sound a little lean with older iPods, which used a rather small series capacitor to couple the output. Conversely, with headphone amplifiers having a high output impedance, the Westone 3 will sound forward in the upper midrange.John Atkinson
Fig.1 Westone 3, electrical impedance (solid) and phase (dashed). (10 ohms/vertical div.)